Under the influence of fungi-causative agents of diseases in plants, pathological processes occur, accompanied by a violation of the structure and physiological functions of the plant or its individual parts, for example, the formation of growths, influxes, changes in respiration, assimilation, enzymatic activity, impaired growth and development, and the death of affected tissues. Externally G. about. R. characterized by one or another type of lesion, which is local or general. Local lesions covering small areas of the plant or its individual organs include spots (cercosporosis (see Cercosporosis) of beets, apple and pear scab, etc.), fungal deposits (Powdery mildew and others), ulcers, pustules (plant rust); to the general - wilting of plants.
G. b. R. transmitted by seeds, tubers, bulbs, roots, cuttings, seedlings, and other parts of diseased plants. The infection can persist in post-harvest residues, in the soil, be carried by the wind, raindrops, animals and humans, containers, agricultural crops. machines and tools. Pathogenic fungi can penetrate into plant tissues through the stomata (miles of grapes), water pores, lentils, through the cells of the epidermis and cuticles (cabbage keel, potato cancer), wounds arising from hail (corn blister smut), sunburn, frostbite (black apple tree cancer), through the cracks. Many insects, damaging plants, open the "gate" of infection, while often carrying pathogens.
Chemical measures consist of treatment with fungicides (see Fungicides) seeds (see Etching), vegetative plants, disinfection of agricultural crops. premises, storage facilities, soil, etc.
Lit .: Naumov N.A., Diseases of agricultural plants, 2nd ed., M. - L., 1952; Natalina O.B., Diseases of berries, M., 1963: Dictionary of phytopathologist, ed. P.N. Golovina, 2nd ed., L., 1967: Tupenevich S.M., Shapiro I.D., Protection of vegetable crops and potatoes from diseases and pests, 3rd ed., L., 1968.
S. M. Tupenevich.
Great Soviet Encyclopedia. - M .: Soviet encyclopedia. 1969-1978 .
See what "Fungal plant diseases" is in other dictionaries:
fungal plant diseases- Table 25. Fungal diseases of fruit: 1 - gray fruit rot of stone fruit (plum); 2 - milky shine of an apple tree; 3 - the same, fruiting of a mushroom on the bark of a tree; 4 - apple scab; 5 - apple fruit rot and mummified ... ...
The processes that occur in a plant under the influence of various causes of pathogens and unfavorable environmental conditions are manifested in dysfunctions (photosynthesis, respiration, synthesis of plastic and growth substances, water flow, ... ...
Plant diseases processes that occur in a plant under the influence of various causes of pathogens and unfavorable environmental conditions are manifested in dysfunctions (photosynthesis, respiration, synthesis of plastic and growth substances, ... ... Wikipedia
See Plant Diseases ... Agricultural Dictionary
QUARANTINE PESTS AND PLANT DISEASES- naib, dangerous pests and diseases, which are absent in the country or spread over part of its territory, but can be included in the dec. countries or penetrate independently, spread and cause damage with. NS. crops. A threat… …
Plant pests and diseases of quarantine significance for the USSR (1986)- I. Not registered in the USSR A. Plant pests 1. Orange scale insect + Unaspis citri 2. White beetle Pantomorus leucoloma 3. Large tangerine fly Tetradacus citri 4. Eastern mealybug Pseadococcus citriculus ... ... Agriculture. Big encyclopedic dictionary
crop diseases- diseases of agricultural plants, pathological processes occurring in plants under the influence of pathogens and unfavorable environmental conditions; manifest themselves in disruption of photosynthesis, respiration and other functions, cause damage ... ... Agriculture. Big encyclopedic dictionary
DISEASES OF AGRICULTURAL PLANTS- patol. processes occurring in plants under the influence of pathogens and unfavorable environmental conditions; are manifested in the violation of photosynthesis, respiration and other functions, cause lesions of the department. organs or premature death. B. s. R.… … Agricultural encyclopedic dictionary
Diseases characterized by the formation of spots of dead cells on leaves, stems, fruits and other parts of plants; a special case of Necrosis. Causes of occurrence: lack of soil nutrients for plants, pollution ... ... Great Soviet Encyclopedia
Books
- Fungal diseases of strawberries and strawberries. Monograph, Govorova Galina Fedorovna, Govorov Dmitry Nikolaevich. The monograph summarizes domestic and foreign experience, the authors present the results of their own long-term research on diseases and breeding characteristics of strawberries and strawberries. ...
Widespread disease. It affects more than 150 plant species, including cotton, vegetables (tomatoes, cucumbers, cabbage), potatoes, cereals (wheat, barley), flax, alfalfa, hemp, tobacco, makhorka, etc.
When damaged, brown, almost black, stripes (root rot) appear on the roots and root part of the stem, which, in conditions of high humidity, are covered with a white or slightly pink bloom of fungal sporulation, consisting of mycelium, conidiophores and conidia. Conidia are colorless, sickle-shaped, with 3-5 transverse septa. Plants wilt and are easily pulled out of the soil. Darkening of the vessels is noticeable on the cut of the stems. The lack of harvest from the disease usually reaches a significant size - not less than 60%.
The causative agent - the fungus Fusarium oxysporum belongs to the order of hyphomycetes, a class of imperfect fungi. The presence of specialized forms and races, confined to certain host plants, was noted.
The main factor in the transmission of the pathogen is soil. Like the causative agent of wilt, the fungus enters the plant through the root system, and then spreads through the vessels. With a high initial population of the pathogen in the soil, the disease is especially dangerous when plants are infected in the early stages of their development.
The seasonal dynamics of the epiphytotic process during the transmission of the pathogen through the soil in the graphic image resembles an S-shaped curve, which, depending on the resistance of the variety, reaches a plateau at different times: when cultivating resistant varieties, it is much earlier and with a lower overall level of disease development than when cultivating susceptible ones. The higher the population density of the pathogen propagules in the soil, the higher the degree of development of the disease. The quantitative indicators of this regularity on different agricultural crops and soils with different suppressive factors are not the same. According to S. Smith and V. Snyder, a very strong development of fusarium of sweet potato was noted in the presence of 5 thousand chlamydospores in 1 g of soil, while in 50 sick plants it was not registered.
French scientists have shown that, on suppressive soils, the infection of pumpkin, cabbage and tomato with the pathogen was absent even in the presence of 2400 propagules / g of soil. On conductive soils, plants died starting from 50 or more propagules / g of soil. The general theoretical soil population index of F. oxysporum and F. solani is higher in conductive soil than in suppressive soil. The introduction of glucose at a concentration of 0.1 mg / g was sufficient to increase the population of species of the genus Fusarium in conductive soil by 1.5 times. For such a population growth in a suppressive soil, the glucose concentration should be 10 times higher. This is due to the fact that the level of fungistatic action is higher in the suppressive soil and is due, according to the authors, to the competition of microbes for energy sources.
Soil suppression is largely due to biotic factors. In some agroecosystems, the suppressors were saprotrophic fungi, fast growing in the soil - Mucor plumbeus, M. hieinalis, Trichoderma viride, Penicillium sp .; when they are introduced into the soil in combination and separately, the suppression of fusarium disease of grain legumes is noted. However, in other environmental conditions, for example, on tomato plantings, soil suppression was mainly due to the bacteria Bacillus subtilis, and on flax crops - Pseudomonas spp., On potatoes and other crops - Trichoderma harzianum alone or in combination with Aspergillus ochraceus, Penicillium Funicolosum. At a concentration of antagonists of 5 · 10 5 soil, the population density of the pathogen decreased from 600 to 200 propagules / g of soil, while in the absence of them, it increased to 5 · 10 10.
An increase in soil suppression can be achieved by selecting certain crops. So, with the introduction of clover, oats, lupine, potatoes into the crop rotation, the ratio between the causative agent of fusarium wilting of flax and saprotrophic microflora of the soil increased from 1:14 to 1:44 - 1:70, which significantly increased the suppressiveness of soils and reduced the death of flax seedlings on 30 40%. At the same time, the population density of the pathogen decreased by 3 times. In permanent crops of flax, the biological balance between pathogenic and saprotrophic species in the soil is disturbed, as a result of which the proportion of the causative agent of fusarium wilt in the total structure of mycoceiosis, including 34 species, in some years increased to 90%, which caused a massive plant disease.
With water deficiency, tissue infection increased many times, slowing down the process of their healing. In addition to the soil, the pathogen remains in plant debris. Moreover, if the infected crop residues are covered with a thin layer of soil, then the formation and dispersal of conidia does not occur. Additional transmission of the pathogen is also possible through seeds, and during the growing season - by airborne droplets using conidia. The importance of this transmission mechanism is especially increasing in protected ground.
The strategy of integrated plant protection against fusarium disease should provide for increasing the suppressiveness of soils and maintaining their moisture content at an optimal level for crops (at least 60% of the full moisture capacity) to interrupt the mechanism of transmission of the pathogen through the soil, as well as the use of seeds free of the pathogen for sowing. The cultivation of resistant varieties is of particular importance.
In order to improve the soil in field crop rotations, black fallow is used, as well as a 5-6-year break in the cultivation of susceptible crops. Systematic incorporation of infected plant debris is important. In protected ground, soil is disinfected at all stages of crop cultivation (disinfection of the main soil, peat mixtures for humus pots and bedding). Effectively growing seedlings without picking in peat cubes, observing culture rotation, enriching the rhizosphere of plants or substrate with antagonists, in particular Trichoderma viride, by pelleting seeds (400 g / c) and additional application of the drug when planting seedlings in the ground and during the growing season (2.7 · 10 10 spores per 1 plant).
An excessively high content of species of the genus Trichoderma in the soils of greenhouse complexes often leads to inhibition of the development of other useful microflora and plants. It is recommended that the proportion of species of this genus in the structure of mycocenosis should not exceed 45%. In this case, the pH values should be in the range of 4.5-7.5. In an alkaline environment (pH 8.5-9.0), Trichoderma practically does not develop.
Suppression of cotton fusarium wilt is achieved when the ratio between the pathogen and the introduced population of Trichoderma is 1: 8 and 1:10, provided that the share of Trichoderma is no more than 30-35% of all fungi.
Field experiments have shown the possibility of a biological method for combating the causative agent of the disease on tomatoes using bacteria-antagonists Pseudomonas mycophaga (strain D-1). Before planting, tomato seedlings were treated by soaking the roots for 3.5 hours in a seven-day bacterial culture liquid (dilution 1: 100), mixed with soil to a mushy consistency. On an area of 20 hectares, the incidence of fusarium wilting decreased from 28.2 to 0.8%; the yield of fruits increased from 181 to 239 centners per hectare, and the cost recovery of the ruble was 16.6 rubles.
In order to avoid the transmission of pathogens through the seeds, they are sorted, cleaned, calibrated and etched with TMTD or foundationol.
The contamination of spring wheat and flax seeds after dressing should not exceed 5%.
To increase plant resistance to infection, it is recommended to avoid growing field crops in soils with low pH and high nitrate nitrogen content. Fertilizers should be applied in accordance with the data of agrochemical cartograms. In protected ground, it is important to maintain optimal conditions for growing cucumbers and tomatoes: soil moisture 85-90% of full moisture capacity, temperature 20-26 ° С (at night not lower than 18-20 ° С, during the day not higher than 30 ° С), watering with heated water (not higher than 25 ° С).
To prevent the transmission of the pathogen by airborne droplets, crops are sprayed with foundation.
If you find an error, please select a piece of text and press Ctrl + Enter.
In practical work, plant diseases are usually classified according to agricultural crops or their closely related groups. Within each culture, diseases are subdivided according to the etiological principle, based on the reasons for their occurrence.
Non-infectious diseases are called diseases caused by unfavorable environmental factors: high or low temperature, lack or excess of moisture and nutrients, unsatisfactory physical and chemical composition of soil, the presence of harmful impurities in the air, etc. These diseases are discussed in detail in manuals on plant physiology, agrochemistry, agriculture, and therefore partially covered in the atlas.
The forms of manifestation of diseases are very different, which greatly complicates their recognition (diagnosis). Quite often, completely different diseases have similar external signs and, conversely, the same disease manifests itself differently depending on the environmental conditions, the environment, the affected organs, the stages of development of the affected plant and pathogen, as well as the nature of the relationships that develop between them.
In practice, various external signs (symptoms) of diseases are grouped into separate types, which makes it possible to make the correct diagnosis of the disease.
The most common types of diseases are: wilting, tissue death, or necrosis, destruction of individual plant organs, rot, the formation of plaque, growths, the appearance of pustules (pads), deformation of plant organs, mummification, release of gum, discoloration of plants.
Withering externally manifests itself in the drooping of leaves, stems and other plant organs. In most cases, it is associated with loss of cell and tissue turgor due to lack of water. The reason for this may also be the blockage of the vessels of plants by pathogens or damage to them with toxins. Often, the plant withers when the roots and stems are damaged by both pathogens and pests. Unfavorable environmental factors can also be the cause of wilting.
Withering away tissues, or necrosis, are characterized by the formation of spots on leaves, stems, reproductive organs, roots. The spots come in various sizes and colors, often surrounded by a border. Often, you can see plaque or other pathological formations on them.
Rot are manifested in the softening and decomposition of plant tissues. In this case, the intercellular substance is often destroyed, as a result of which maceration (separation) of cells occurs.
Raids on plant organs are observed in fungal diseases. Often they appear due to the growth of mycelium on the surface of affected plants or the formation of sporulation of fungi. The color of the plaque is different.
Pustules it is customary to call convex pads of various sizes and colors, which consist of sporulation of the causative agent of the disease. Most often they appear with the development of rust diseases.
Deformation characterized by a change in the shape of plant organs under the influence of the causative agent of the disease. In this case, the leaves and stems can be shortened, strongly branched or accrete. Sometimes the shape of the flowers changes and they become sterile.
Growths, or tumors, appear due to the abnormal growth of individual parts of plants under the influence of the causative agent of the disease. There are also growths consisting of the body of the fungus.
Mummification- a type of disease in which the organ of the plant is densely penetrated by the mycelium and often turns into sclerotia.
Highlighting gum observed when plants are damaged mainly by fungi and bacteria. It is characterized by the release of sticky mucus of light or brown color. Sometimes the cause of gum disease is damage caused by agricultural implements and pests.
The change colors tissues are more often observed on leaves, stems and inflorescences under the influence of pathogens, especially viral and mycoplasma, as well as in case of malnutrition of plants. Genetic diseases can also be the cause of this phenomenon. The change in tissue color is associated with a violation of the structure and physiological functions of chloroplasts. This type of disease manifests itself in the form of chlorosis, mosaic leaves, variegated color and general yellowing.
Asymptomatic(latent) diseases are more common when plants are damaged by some viruses and mycoplasmas and are characterized by the absence of external signs of a pathological process. Latent diseases can cause poor fruit production. Sometimes there is a temporary disappearance of the symptoms of the disease, especially in hot weather, but with a cold snap, they reappear.
It should be noted that the listed types of diseases are not limited to the whole variety of manifestations of pathological changes in plants. In phytopathological practice, there are often cases when the external signs of several diseases are almost the same, but the causes of their occurrence and pathogens are different. Therefore, in order to accurately determine the disease, in addition to an external examination of the affected plant, special studies are needed in order to establish the pathogen and sources of infection. In most cases, the external signs of the disease are supplemented by microscopic examinations and morphological data on the pathogen. In some cases, methods of fixation and staining of sections of affected tissues for histological and histological-chemical studies are used.
For a more correct identification of the pathogen and identification of sources of infection, cultural and biological studies are often used.
Cultural studies of the causative agent of the disease consist in isolating it into a pure culture, studying it by morphological and biochemical characteristics, as well as biological characteristics.
Biological studies are carried out when studying the specialization of the pathogen in relation to the affected plant and determining the degree of susceptibility of the latter to the pathogen. In these cases, artificial infection of plants with the pathogen is carried out, followed by a comparative study of the symptoms of damage and other features of the course of the disease. Knowledge of the physiological and biochemical characteristics of a diseased plant is of great help in this matter. It is also important to identify the factors that promote or inhibit the development of the disease.
Mushrooms. Previously, they were considered an independent department of the plant kingdom. Currently, researchers attribute mushrooms to the kingdom of living organisms. Mycota, occupying an intermediate position in taxonomy between animals and plants.
They are brought closer to the animal kingdom by the presence of urea in the metabolism, chitin in the cell membranes and the formation of a reserve product - glycogen. However, in terms of the way of nutrition (absorption, not swallowing food) and the characteristics of growth, they are closer to plants.
All fungi belong to heterotrophic organisms, that is, they are unable to synthesize organic compounds and feed on various organic substances found in nature.
Fungi that settle on dead plants or other organic debris are called obligatory saprophytes. Many of them contribute to the circulation of substances in nature and therefore are useful, others can settle on agricultural products and spoil it.
Depending on the structure of the vegetative body, mushrooms are divided into two sections - Myxomycota and Eumycota(Hawksworth et al. 1983). In Myxomycota, the vegetative body consists of a protoplasmic amoeba-like mass. Most of the representatives of this department are saprophytes, living mainly in forests (slime molds). However, among them there are also causative agents of dangerous diseases of cultivated plants - keels of cruciferous crops and powdery scab of potatoes (representatives of the class Plasmodiophoromycetes order Plasmodiophorales).
Representatives Eumycota vegetative body - mycelium, consisting of thin hyphae (filaments) that grow and can branch. Depending on the structural features of the mycelium, they are divided into lower and higher mushrooms. In the lower mycelium is well developed, but not divided into cells, therefore it is called non-segmented, or unicellular. In higher fungi, it consists of many cells and is called articular, or multicellular (Fig. 1).
Fig. 1. Types of mycelium: 1 - in the form of naked plasma in the cell of the host plant; 2 - well developed, but not divided into cells (non-septic); 3 - multicellular.
Depending on the location in the plant, the mycelium can be internal, or endophytic (in most fungi), and superficial, or exophytic (mainly in mealy weeds and some others).
The hyphae of the endophytic mycelium are more often located in plant tissues between the cells, and only some fungi with their hyphae penetrate directly into the cells. In most cases, special outgrowths of various shapes, which are called haustoria, penetrate into the cells from the mycelium (Fig. 2). With their help, fungi absorb nutrients from the affected plants, as well as water. 
Fig. 2. Forms of haustoria in mushrooms: 1 - Albugo; 2 - Erysiphe; 3 - Peronospora.
Fungal cells have a nucleus, a protoplasm, and almost always a shell. The nuclei are round or slightly elongated, 2-3 microns in size, surrounded by a nuclear membrane. Depending on the type of fungi and the stages of their development, one cell can contain from one to several nuclei.
The protoplasm in young fungal cells usually fills almost the entire cavity, and it contains small vacuoles in the form of rounded vesicles. In older cells, protoplasm, as a rule, is located in a thin layer near the membrane, the center of the cell is occupied by a large vacuole, through which thin protoplasmic strands pass in different directions.
The cell membrane in most fungi is initially colorless, and with age it often becomes pigmented and thickened.
The mycelium of many fungi can change and take various forms, the main ones of which are:
sclerotia- dark solids, consisting of a dense plexus of hyphae with a low water content (up to 10%) and a significant supply of nutrients;
stroma- a dense plexus of the mycelium of the sclerocial type, penetrating the organs of plants. On the surface or inside the affected plant organs, spore-bearing organs of fungi are formed on the stroma;
chlamydospores- small rounded areas of hyphae, devoid of vegetative mycelium. They contain many nutrients, little water, are often covered with a dense, thickened, sometimes pigmented membrane and in most cases are able to withstand adverse environmental conditions;
gems are formed in the same way as chlamydospores, but differ from them in the instability of forms;
cords- cord-like formations, consisting of parallel placed hyphae, which often grow together.
In some fungi, the cords contain hyphae of a homogeneous structure, in others, their differentiation is observed into the outer ones, which are thin and strong, and the inner ones, which are wider with unevenly thickened walls;
rhizomorphs- the plexus of the mycelium, in which the superficial hyphae are dark in color, and the inner ones are light;
mycelial films- dense plexuses of mycelium formed on the surface or inside plant tissues.
Mushrooms reproduce vegetatively, asexually and sexually. Vegetative reproduction occurs by separate hyphae or mycelium and its modifications, asexual - with the help of special spores formed on special outgrowths of the mycelium. Spores can be of endogenous or exogenous origin.
The first of them are unicellular and are of two types - sporangiespores (immobile), covered with a membrane, and zoospores - mobile, with one or two flagella. The receptacles of sporangiespores are called sporangia, and the outgrowths on which they develop are called sporangiophores (Fig. 3). In zoospores, zoosporangia and zoosporangiophores, respectively (Fig. 4). 
Fig. 3. Asexual Reproduction Organs of Zygomycete Fungi Rhizopus nigricans: 1 - sporangiophores with sporangia; 2 - sporangium (greatly enlarged).
Fig. 4. Zoosporangia and zoosporangiophores: 1 - germination of zoosporangium with the formation of zoospores in fungi of the genus Olpidium; 2 - zoosporangium fungi of the genus Saprolegnia... Zoosporangia on zoosporangiophores of peronosporous fungi: 3 - Pythium; 4 - Pseudoperonospora; 5 - Phytophthora.
Exogenous spores are formed directly on the surface of special outgrowths and are called conidia, and the outgrowths themselves are conidiophores (Fig. 5). In some fungi, conidia with conidiophores appear in special containers - pycnidia (Fig. 6). 
Fig. 5. Conidiums with conidia in fungi of the genera: 1 - Oedocephalum; 2 - Verticillium; 3 - Sterigmatocystis; 4 - Penicillium; 5 - Erysiplie; 6 - Alternaria.
Fig. 6. Pycnid with pycnospores of fungi of the genus Septoria.
In these cases, conidia are often referred to as pycnospores. Sometimes conidiophores are collected in bundles and then they are called koremia (Fig. 7). A number of fungi form a continuous layer of short conidiophores with conidia located on a denser plexus of hyphae, the so-called bed (Fig. 8). Mushrooms from the family Tuberculariacea Conidiophores with conidia are formed in the form of loose mucous tubercles - sporodochia or the same tubercles, but merged with each other (pionnota). 
Fig. 7. Koremia with conidia of fungi of the genus Sphaerostilbe.
Conidia are unicellular and multicellular, and also vary in shape, color, and size.
Sporangiophores are usually unbranched, while zoosporangiophores and conidiophores often have branches with different endings.
Sexual reproduction is carried out by spores, which are formed when two cells of different sexes merge.
In lower fungi, when two mobile vegetative zoospores (or gametes) merge, a zoosporangium, or cyst, is formed. When two cells of different shape and size merge, an oospore appears, and when cells of the same shape merge, a zygospore appears. These spores often have a double shell with various inlays (Fig. 9).
Higher marsupial mushrooms reproduce by forming bags with ascospores (asok with ascospores). In some of them, bags can develop directly on the mycelium, but in most they are formed in special fruit bodies (plexus of hyphae of the mycelium) or on their surfaces.
Fruiting bodies of fungi are of three types: clestothecia, perithecia and apothecia.
Cleistothecia- closed (closed), often rounded, with pendants of different shapes. Inside their bags are arranged, as a rule, randomly or in a parallel bundle. The latter are released after destruction or rupture of the sheath of the cleistothecium (Fig. 10). 
Fig. 8. The bed (continuous layer) of conidiophores with conidia on a dense plexus of mycelium hyphae in fungi of the genus Gloeosporium.
Fig. 9. Oospores and zygospores: 1 - antheridium and oogonia before fertilization and oospore formation; 2 - formed oospore; 3 - the sexual process and the development of the zygospore; 4 - mature zygospore and its germination.
Fig. 10. Cleistothecia with bags and ascospores in fungi of different genera of the family Erysiphaceae: 1 - Podosphaera; 2 - Sphaerotheca; 3 - Erysiphe; 4 - Microsphaera; 5 - Trichocladia; 6 - Phyllactinia; 7 - Uncinula; 8 - Leveilluia.
Perithecia- fruiting bodies with a narrow aperture at the apex (Fig. 11). The bags in them are usually formed by a bunch, and in some mushrooms they are located in the plexus of the mycelium, which is called the somcostroma. In shape, the somcostroma resemble perithecia and are often called pseudothecia. 
Fig. 11. Perithetia with bags and ascospores of mushrooms of various genera: Melanomma : 1 - perithecia; 2 Herpotricha : 3 - perithecium; 4 - bag with ascospores and paraphysis; Pleospora : 5 - perithecia; 6 - bag with ascospores.
Apothecia- open, mainly cupped or saucer-shaped fruiting bodies, on the surface of which bags develop in a wide layer (hymenium), and between them are infertile hyphae - paraphysis (Fig. 12). 
Fig. 12. Apothecia with bags and ascospores in mushrooms of various genera: Calloria; 1 - apothecia; 2 - a bag with ascospores and paraphysis; Erinella : 3 - apothecia; 4 - bag with ascospores
In higher basidiomycetes, the sexual process ends with the formation of basidia with basidiospores (Fig. 13). Basidia are clavate or cylindrical, multicellular or unicellular (phragmobasidia). Each basidium usually has four unicellular rounded ovoid or filamentous basidiospores. 
Fig. 13. Basidia with basidiospores in mushrooms: 1 - homobasidial; 2 - heterobasidialysh; 3 and 4 - teliomnaceous
All signs of vegetative, asexual and sexual reproduction of fungi are taken into account when classifying them.
In the Department of Epicoza, pathogens of agricultural crops are represented by three classes of lower (chytridiomycetes, oomycetes, and zygomycetes) and higher (marsupials, basidiomycetes, and imperfect) fungi.
Zygomycete class ( Zygomycetes) also includes mushrooms with a well-developed non-segmented mycelium. During asexual reproduction, they form sporangiespores (in sporangia) or conidia. The sexual process is isogamous (fusion of two motionless morphologically identical cells) with the formation of a zygospore. Most of these fungi are saprophytes that live on plant debris, but some of them can cause diseases of cultivated plants and insects.
Class marsupials ( Ascomycetes) unites more than 25 thousand mushrooms with multicellular (septate) mycelium. Many have asexual (conidial) sporulation. Sexual reproduction proceeds with the formation of bursae and bursa-spores. This class is subdivided into three subclasses:
fruiting- bags are formed in the fruiting bodies; there are many pathogens of field crops among them;
abdominal, or loculoascomycetes - bags, one by one or more often in groups, are formed in the cavities of the sumcostrom (pseudothecia); this subclass also contains fungi that cause dangerous diseases of field crops.
Class basidial ( Basidiomycetes) unites about 30 thousand species, in which the mycelium is multicellular, and the main organ of sporulation is the basidium, which is formed on the binuclear mycelium as a result of the sexual process. Depending on the type of basidia, this class of mushrooms is divided into three subclasses: homobasidial(Homobasidiomycetidae - unicellular basidia, clavate, with basidiospores located at the tops;
heterobasidial (Heterobasidiomycetidae) - multicellular basidia, basidiospores are located one on each cell;
sclerobasidial, or teliomycetes ( Sclerobasidiomycetidae or Teliomycetidae), - basidia are unicellular or multicellular and are always formed from germinating spores, which are now commonly called teliospores.
Among the latter, smut, united in order Ustilaginales, and rust fungi from the order Uredinales.
Smut fungi affect various parts of plants, but more often their generative organs. At the same time, the destroyed tissues darken, acquire a kind of burnt appearance, hence the name of these diseases. The dark color of the affected areas is given by the dark-colored teliospores formed in large quantities. Previously, they were called chlamydospores, since they are formed by compaction and isolation of the contents of individual cells of the vegetative mycelium and are covered with a thick-walled membrane. However, in smut fungi, such spores do not form a vegetative mycelium during germination, but give a basidium, where the nucleus phase changes.
Rust fungi mainly affect the aboveground organs of plants, forming rusty-brown, orange-yellow or dark brown clusters of spores on them, which in most cases protrude outward through breaks in the epidermis or cortex of the affected organs.
In the development cycle of rust fungi, five types of sporulation have been established, which are usually denoted by the following numbers: 0 - spermogonia with spermations; I - aecia with eciospores (etsidia with eciospores); II - uredinia with urediniospores (uredopustula with urediospores); III - telia with teliospores (teliopustules with teliospores); IV - basidia with basidiospores.
Each type of sporulation has its own morphological and biological characteristics.
Many pathogens of rust diseases of field crops pass the full cycle of their development on two types of plants, therefore they are called dioecious, or different hosts. Some of the rust fungi have lost this ability and develop on one plant, therefore they are called monoecious.
Certain types of rust fungi have specialized forms that affect certain plants, as well as physiological races and biotypes that differ in their virulence to certain varieties of grain crops.
Imperfect fungi combine more than 25 thousand species with a well-developed multicellular mycelium, most of which reproduce asexually (conidia) or vegetatively (mycelium). Some of them, under certain environmental conditions, are capable of sexual reproduction of bursae with ascospores or basidia with basidiospores.
Imperfect mushrooms are divided into orders according to the type of sporulation (on free or accrete conidiophores, in beds and pycnidia). The structure of the spores, the color and the number of cells in the spore are also taken into account. Accepted two classifications of imperfect mushrooms - R. A. Saccardo and A. A. Potebni, which are used in the atlas.
Bacteria and actinomycetes. Bacteria are unicellular organisms with protoplasmic content. In young cells, the protoplasm is homogeneous; in older cells, vacuoles are found. Bacteria do not have a well-formed nucleus and their nuclear matter is in a diffuse state.
Bacteria come in various shapes: spherical, rod-shaped, spiral, filamentous, and branched. They multiply by simple division. All bacteria that cause plant diseases are rod-shaped. They are single, connected in pairs or in the form of chains. In some bacteria, flagella are located polarly or peritrichially (Fig. 14). For the diagnosis of bacteria, their Gram staining is important: gram-positive - firmly hold the paint and acquire a dark purple, and gram-negative - red. 
Fig. 14. Bacteria (under an electron microscope): 1 - with polar flagella; 2 - with peritrichial
For the determination of bacteria, in addition to morphological, cultural and physiological characteristics are also of great importance: the characteristics of growth on nutrient media, the shape and color of colonies, the relation to molecular oxygen, sources of nitrogen, carbon, gelatin liquefaction. Often all these signs are supplemented by data from serological studies (use of immunological sera, etc.).
For the final determination of the bacterial pathogen, it is necessary to artificially infect the host plant and study the symptoms of the disease. Among the bacterial pathogens of field crops, bacteria from the genera Pseudomonas, Xanthomonas, Aplanobacterium and Corynebacterium.
Actinomycetes, or radiant fungi, occupy an intermediate position between fungi and bacteria. Their vegetative body consists of a thin branched non-septic mycelium, which brings them closer to lower fungi. However, the nuclear matter in these fungi, like in bacteria, is in a diffuse state. Actinomycetes reproduce by pieces of mycelium and spores, which are formed by segmentation of the spore-bearing branch into separate sections with transverse septa, or fragmentation - by the disintegration of its contents into individual cells (Fig. 15). 
Fig. 15. Reproduction types of actinomycetes: 1 - segmentation; 2 - fragmentation
Actinomycetes cause diseases in beets, potatoes and other crops.
Viruses. Viruses include the smallest pathogens of infectious diseases that multiply only in living cells of plants (or animals). Almost all viruses are so small that they pass through bacterial filters, which is why they are often called filterable viruses. Distinguish between rod-shaped, filamentous, rounded, spherical and spiral viruses (Fig. 16). 
Fig. 16. Types of viruses (under an electron microscope): 1 - rod-shaped; 2 - threadlike; 3 - spherical; 4 - spiral.
Their size is determined in millimicrons (mmkm), nanometers (nm), or angstroms (A): 1mmkm = 1nm = 10 -9 m, 1A = 10 -10 m.
Each virus of the same species has certain characteristics, especially pronounced in their dormant forms, which are often called virions, or virospores.
Modern research methods make it possible to isolate viruses from the juice of a diseased plant, purify and obtain them even in crystalline form. The crystalline state of viruses does not reduce their activity. All phytopathogenic viruses are nucleoproteins consisting of nucleic acid (mainly RNA) and proteins, which include about 20 amino acids, linked by a peptide bond.
An important feature of viruses is the ability to reproduce their specific structures. Phytopathogenic viruses multiply very quickly in living cells of susceptible plants or in their isolated tissues growing in artificial nutrient media. They spread with the help of various insect vectors (aphids and others), as well as during plant grafting or inoculation.
Most phytopathogenic viruses are not very specialized (they infect many plants within botanical families), but some of them infect plants within the same botanical genus.
The classification of viruses is based on the concept of their origin and evolution. Many viruses currently have various synonyms. More often, the generic name for the virus is given from the generic name of the host plant, then the word virus is written, the serial number of its detection and the surname of the author who first described this virus. For example, the causative agent of winter wheat mosaic is Triticum virus 8 Zazurilo et Sitnicova, where Triticum- the generic name of wheat, virus 8- the virus that was detected on wheat eighth, a Zazurilo et Sitnicova- the names of the authors who first described it and proposed such a name.
In recent years, in addition to viruses, the so-called viroids, which have an extremely low molecular weight, have been identified. Several diseases of viroid etiology have been described.
Mycoplasma bodies(MPT) as causative agents of diseases have recently been discovered mainly in the phloem, sieve tubes and plant parenchyma. These are predominantly ellipsoidal or rounded, sometimes elongated or curved, with constrictions, heteromorphic formations (Fig. 17) with an average size of 200-300 nm, occurring singly or in clusters. Instead of a shell, they are surrounded only by a double membrane with a thickness of 7-8 nm and in appearance are very similar to degenerating mitochondria, as a result of which they could not be identified for a long time. 
Fig. 17. Mycoplasma bodies (under an electron microscope)
MPT can be propagated and cultivated on complex artificial nutrient media.
All MAT are spread using a carrier (vector). In insect vectors (mainly leafhoppers), they can multiply and accumulate.
Viruses and MPTs persist mainly in vegetative plants and insects. Only a few of them can be found in seeds, plant debris and soil.
Fig. 18. Scheme of the structure of phytonematodes (according to A. A. Paramonov and F. I. Bryushkova, 1956): a - female; b - male; 1 - oral cavity; 2 - the corpus of the esophagus; 3 - medium bulb; 4 - rear bulb with a crushing apparatus; 5 - nerve ring; 6 - intestines; 7 - ovary; 8 - oviduct; 9 - uterus (front and back); 10 - testis; 11 - the zone of sperm maturation; 12 - seed tube; 13 - ejaculatory canal; 14 - spicules; 15 - steering wheel; 16 - the wings of the bursa with ribs.
The body of the nematodes is non-segmented and covered with a smooth or annular cuticle. Their length is from 0.5 to 2 mm, and their diameter is usually about 15-20 microns. In some species, females swell when laying eggs and then their diameter reaches 200-400 microns or more. The nematode consists of a head, body and tail. In the head part there is a nervous, or labial ring, in the center of which the oral cavity and post-labile rings are located, varying in shape and being important in the diagnosis of species. The body occupies most of the nematode (from the head to the anus in females and larvae, or to the cloaca in males). The rest (tail) is not the same in shape in different species, which is also taken into account when determining them.
In the oral cavity there is a so-called stylet, with the help of which the nematode pierces plant cells. The esophagus consists of a body with a muscular middle bulb, an isthmus surrounded by a nerve ring, and a posterior (cardiac) glandular part. The enzymes of the glands through the stylet are partially secreted into the external environment and contribute to the dissolution of the contents of the cells, and the contractions of the bulb help the absorption of food.
Nematodes reproduce sexually, followed by laying eggs in a free form (in stems), in a sticky gelatinous sac (in galls), or eggs accumulate in the body of a female that turns into a cyst (in cyst nematodes).
An indispensable condition for the development of nematodes is high soil moisture. Temperature is also important, but its criteria for different types of nematodes are not the same.
Many nematodes can easily tolerate drying and low temperatures.
Lighter soils are more suitable habitats for most nematodes that feed on plant roots.
The root secretions of some plants stimulate the release of larvae from the eggs, while others scare away or even cause their death. This feature should be taken into account when developing protective measures against nematodes. Phytohelminths can be destroyed by predatory nematodes and some fungi.
Known nematodes - carriers of viral, bacterial and fungal plant diseases.
The taxonomy of nematodes as representatives of the animal world is covered in special literature. The most pathogenic species in relation to field crops belong to three families - aphelenchoidids, tylenchids, and heteroderids.
When plants are affected by nematodes, the emergence of seedlings and plant growth are often slowed down. Affected plants bloom poorly and bear fruit, and often completely die.
A third example is Fusarium culmorum, which also attacks the roots of seedlings of a wide variety of plants (asparagus, cereals). It is not found in the soil as free mycelium, unlike Pythium and Rhizoctonia, since its spores germinate only when a suitable substrate is available. All these species belong to saprophytic "sugar" mushrooms. They preferentially attack young, already damaged or weakened roots and never disappear from the soil of cultivated fields.
Fungi that damage vascular vessels are found primarily in the Fusarium oxysporum group and among the Verticitlium species. The fungi that cause tracheomycosis penetrate the roots of the host plant, in which they, however, immediately germinate to the vascular vessels (xylem).
This leads to wilting of plants, which does not occur as a result of mechanical blockage of blood vessels, but is caused by the action of the secretions of the fungus on the plants.
Fungi primarily secrete special wilting toxins (fusaric acid, lycomarasmin), which disrupt the osmotic functions of living cells, mainly in the leaves. Secondly, they contain pectinase, which destroys protopectin - the main substance of the median plates in the vessels. The pectic acids and other products of partial hydrolysis thus liberated increase the viscosity of the xylem juice and thus impede the supply of water.
Since the rest of the host plant tissues are resistant to wilting pathogens, only a few, less resistant vessels are affected. Only after the plant dies off and the fungus leaves the conducting vessels, the affected root can infect neighboring roots. Forcibly removing the damaged plant leaves the infected parts of the roots in the soil, and the disease spreads even faster. The introduction of nitrogen fertilizers stimulates the development of fungi that infect blood vessels, directly enhancing their nutrition.
Since fungi can exist as saprophytes, they do not disappear even with a change in crop rotation. Tracheobacteriosis is widespread, the causative agents of which can be, for example, Erwinia tracheiphila, Corynebacterium michiganense, Xanthomonas campestris, or Pseudomonas solanacearum. These bacteria also contain pectinase and even cellulase, so the process of wilting of plants proceeds in the same way as when infected with fungi.
However, all these fungi can for many years be in the form of dormant spores (archycetes, phycomycetes) or sclerotia (ascomycetes, imperfect fungi) in the absence of their host, until a suitable forage plant appears again.
Low temperatures, drought and poor soil aeration allow fungi to cope better during the cold season. Likewise, dormant cabbage keel spores survive longest in relatively dry alkaline soils. These conditions limit the spontaneous germination of spores, which would naturally damage the fungi in winter.
If, with tracheomycosis, the growth of the fungus inside the plant does not depend on the state of the soil, then for ectotrophic fungi developing in the roots, soil conditions are always decisive.
In addition, they only damage seedlings, so the period of possible infection is relatively short. The opposite is observed in the Ophiobolus fungi. True, the processes in the soil are so complex that it is rather difficult to predict the impact of certain measures, for example, fertilization. With each new combination of external factors, conditions can develop completely differently.
Phytopathogenic fungi significantly reduce the decorative effect, viability, as well as the yield and quality of food plant species, and in fruit trees and berry plants, in addition, they also reduce the terms of their economic use.
Spores of fungi can persist for a very long time in post-harvest residues, in the soil, carried by the wind, raindrops, animals and humans, containers, machines and tools. That is why it is so important to keep everything clean, and always carefully and carefully dispose of plant residues in your area.
The presence of various fungi on plants is evidenced by a change in the usual green color of the leaves, the characteristic color of buds and flowers. It also manifests itself in the appearance of a cotton-like outgrowth on the wood of soft or softened areas on the plant, spots of different colors or gray "fluff" on the leaves, black soot spots or dusty red "spots", intersecting gray "filaments" of fungal hyphae on the soil surface. On diseased fruits, rotten leaves and rotten wood, fungi can look like a loose "lace" or powdery mass, like a "film" or "crust", or have the appearance of plates or scales. Under the influence of developing fungi, plant tissues become covered with plaque, spots or atypical "veins". Then the plant parts affected by the fungi begin to die off and decompose; or, conversely, curl, dry out, deform and crack. The sooner diseased plants (or their parts) are identified, the easier and easier it is to fight fungal diseases.
What can be done in order to, if not get rid of fungal diseases, then at least significantly reduce their likelihood. There is, for example, such a well-known agronomic technique as liming the soil. In this case, the soil is alkalized and thereby the risk of damage to plants (for example, cabbage - keel) is reduced. With a lack of boron in the soil, beets often develop heart rot. Excessive application of nitrogen to the soil with a lack of phosphorus and potassium enhances the defeat of cereals by rust, and potatoes - by late blight.
At home, liquid for disinfecting plants, pots and plant care equipment can be prepared from a solution of copper sulfate with the addition of one of the available insecticides. To obtain a disinfectant liquid, 2 g of Actellik (or 1 g of Decis; or 1 g of Karate) are added to a 0.5% solution of copper sulfate (5 g per 1 liter of water). You can use an aqueous solution (0.1–0.2%) of potassium permanganate (potassium permanganate) for processing inventory, spring tillage.
Prolonged rains and high soil moisture, stagnant moist air in thickened plantings often lead to fungal diseases of garden plants. One of the preventive methods is to keep the garden clean. All carrion should be collected regularly, and at the first signs of fungal diseases, immediately start treating diseased plants. Specimens severely affected by the disease that do not respond to treatment must be burned.
When plants propagate and care for them, charcoal and other means are used to prevent the penetration of pathogenic fungi into plant tissues. Growth bioregulators, such as Energen, help to strengthen the immunity of plants. Energen increases the yield by 30-40%, stimulates the growth and development of plants, protects against adverse factors, frost, drought, increases the survival rate of plants during transplantation, and also reduces the content of nitrates in fruits.
If the plants do get sick, then they have to resort to their treatment with suitable fungicides, or, in order to avoid violent infection and death of many plants. especially in the collection, to destroy diseased specimens.
Essential oil, in the form of spraying or treating plants with an alcoholic solution of essential oil (1: 100), has a powerful effect on the reproduction and spread of harmful fungi. The essential oils of oregano, thyme, monarda, lavender, patchouli, hyssop, marigolds, eucalyptus, cedar and some other plants have pronounced antifungal properties. Alcohol extracts of plants such as onions, garlic, marigolds, yarrow, tansy can be used as an antifungal agent, which are cooked in a proportion (1:10, and then, before use, they are also diluted in water 1:10).
Plant diseases caused by fungi
BLACK LEG is the most common disease affecting seedlings and seedlings of most crops. When young plants are affected by the "black leg", white spots and constrictions are formed in the lower part of the stem, as a result of which the plants wither and die.
ROOT ROTS - often affect adult plants: they begin to lag behind in growth, turn yellow, and then partially or completely die. Species affected by root rot should not be planted in soil where fresh manure has been introduced, as well as in places where plants affected by this disease were in previous years.
FUSARIOUS WILT - brown necrotic spots appear on the leaves and stems. The plant stagnates and then dies. Plants of the same species cannot be planted in their place for several years. In the germination phase, decay of the roots, the stem at the root collar and cotyledons is observed. Seedlings turn brown and often die before reaching the soil surface.
Mealy dew - on the underside and / or on the upper side of leaves and petioles, a white mealy bloom appears, and then dark dots.
PERONOSPOROSIS or downy mildew is widespread in areas with sufficient moisture. The disease affects all aboveground organs. The disease manifests itself in two forms: general oppression of plants (diffuse damage) and leaf spot (local damage).
RUST - widespread. The disease often manifests itself in the second half of the growing season of plants. The disease develops most strongly in warm and humid years.
Fungicides - drugs used against fungal diseases
These drugs are divided into a number of groups: inorganic (preparations based on sulfur, copper and mercury) and organic. They are divided into preventive (they stop the development and spread of the pathogen in the place of accumulation) and therapeutic (cause the death of the fungus after infecting the plant with it). Fungicides are also contact and systemic. When treating plants, contact fungicides remain on the surface and cause the death of the pathogen upon contact with it. The effectiveness of contact preparations depends on the duration of action, the amount of fungicide, the degree of retention on the treated surface, photochemical and chemical resistance, weather, etc. metabolism in the plant. Their effectiveness is mainly determined by the rate of penetration into plant tissues and to a lesser extent depends on meteorological conditions. The nature of the use of fungicides is different: seed dressing, for processing soil and plants, both during dormancy and during their growing season.
With the systematic use of the same fungicides, their effectiveness may decrease due to the formation of resistant races of the pathogen. To prevent this phenomenon, it is necessary to strictly observe the dose of the drug and alternate fungicides.
Biological fungicides: Fitosporin, Barrier, Zaslon, Fitop, Integral, Baktofit, Agate, Planzir, Trichodermin. Biological fungicides are characterized by low toxicity and high efficiency.
Acrobat M, ditan M-45, ridomil, sandofan - have a systemic, penetrating and contact effect, acting against a wide range of phytopathogenic fungi.
Bordeaux liquid (one of the most effective and oldest remedies) is effective in combating rust, gray mold, spotting, late blight, scab and downy mildew. For spraying plants during the growing season, a 1% solution is used, for spraying woody plants before bud break, a 3-5% concentration is used.
Glyocladin - Analogue of Trichodermin. Biological fungicide for suppressing fungal pathogens in the soil.
Potassium permanganate (potassium permanganate) is used for dressing seeds, bulbs, corms, plant rhizomes at a concentration of 0.1-0.15% for two hours. It can be used for health-improving watering of seedlings, seedlings and adult plants under the root in the fight against black leg, fusarium, bacteriosis. Used for disinfection of equipment and tools.
Oxyhom has contact and systemic activity. It has a destructive effect on pathogens in all stages. Provides long-term therapeutic and prophylactic effect.
Soda ash (linen) is used to combat powdery mildew. For spraying, prepare a 0.3–0.5% solution. For better adhesion to plants, laundry soap is added to the soda solution.
Tattu strengthens the immune system of the plant and is well tolerated by plants during the entire growing season.
Tilt, Topaz, Skor, Bayleton, Alto, Impact, Vectra - have a systemic, penetrating and contact effect, acting against powdery mildew and rust fungi.
Trichodermin. Biological fungicide for the treatment and prevention of plant root infections. The fungal mycelium growing in moist soil from spores suppresses about 60 types of soil pathogens that cause root rot.
Fitosporin-M is a microbiological preparation designed to protect plants from a complex of fungal and bacterial diseases.
Fundazole is a fungicide and dressing agent with a wide spectrum of systemic action against a large number of fungal diseases of seeds and plants.
Copper oxychloride is effective against the same diseases as Bordeaux liquid. Used in 0.4–0.5% concentration. Do not add soap to the working solution.
When purchasing fungicides, instructions for use are always attached to them. It is very important to accurately follow the recipe for dilution, use of the recommended doses, timing and rules of application.
Alexey Antsiferov, Candidate of Agricultural Sciences,
Corresponding Member of ANIRR
